1. Field of the Invention
This invention relates to fluid valve apparatus and, in particular, to float actuated fluid valves.
2. Description of the Prior Art
It is well known in liquid dispensing systems that air eliminators may be employed to automatically remove air or other gases entrained within a flowing stream of liquid. It is necessary to remove such gases from the liquid flow in order to prevent erroneous readings of the actual volumetric flow of the liquid taken by a metering apparatus that is usually connected downstream of the fluid valve assembly.
A typical example of prior art eliminators for removing air from a liquid petroleum dispensing system is the valve apparatus shown in U.S. Pat. Nos. 3,536,091 and 3,536,099 to C. D. Erickson, both of which are assigned to the assignee of the present invention. The prior art valve apparatus as exemplified by the above-mentioned patents includes first and second cylindrical valve members, one of which is mounted in a stationary position within a valve housing and the second of which is rollably movable along the surface of the first. Suitable fluid ports are provided within the stationary cylindrical valve member. The cylindrical valve members are interconnected by first and second pairs of involuted, opposed bands which are fixed at their opposite ends to the cylindrical members. One pair of bands is connected to the stationary member and extends between the two members and around the generally opposite surface of the second cylindrical member so that while the first pair of bands are in a first position wrapped around the first cylindrical member, the fluid ports are covered thereby. The second pair of bands extends in the opposite direction between the two cylindrical members. Relative rolling movement between the two cylindrical members causes the opposed pairs of flexible bands to inversely engage the surfaces of the members. That is, the pair of bands which in the closed position covered the fluid ports is unwrapped or peeled from the first cylindrical member and wrapped about the second cylindrical member as the cylindrical members are rolled relative to one another. Simultaneously, the second pair of flexible bands, initially wrapped about the second cylindrical member, is unpeeled therefrom and is wrapped in engaging contact with the first cylindrical member.
Although the prior art valves were effective for the purpose provided, particular care had to be given to the selection of materials utilized for the flexible bands and especially to the material's strength properties. Such care is required because the bands, as they are rolled and unrolled from one cylindrical valve member to another, experience a reverse bending stress. That is, the portions of each band which are initially subjected to a compressive load are quickly unloaded and then immediately subjected to a tensile load. Conversely, portions of the bands which are initially loaded with a tensile force are quickly unloaded and immediately subjected to a compressive load. This rapid change in the stresses imposed upon the flexible bands has a tendency to cause premature fatigue failure unless proper precautions, such as the use of an appropriate material of an appropriate thickness, are taken to insure the long-term viability of the flexible bands. Of course, such precautions are expensive.
The prior art fluid valves also are characterized by their excessive complexity, due to the provision of the support structure necessary for facilitating the rolling movement of one cylindrical member relative to the other. Further complexity is entailed in prior art valves by the necessity of providing biasing members which provide a variably compensating bias force on the band members to stretch the bands taut over the cylindrical surfaces of the valve members.
It is advantageous, therefore, to provide a fluid valve apparatus in which flexible bands are tautly stretched in tension about a cylindrical surface of a stationary valve member. It is of further advantage to provide a fluid valve apparatus in which flexible valve bands are not subject to reverse bending stresses as the bands are moved from a first, closed, to a second, open, position. It also is advantageous to provide flexible guide bands which similarly are not subject to reverse bending stresses as these bands move from a first to a second position. It is also advantageous to provide a valve that is less costly from a material and manufacturing viewpoint. It is of even further advantage to provide a valve apparatus wherein the operating life expectancy of fluid valve apparatus is increased due to the elimination fatigue stress imposed upon the bands.
It is advantageous to provide a less complex and more streamlined fluid valve actuating structure which utilizes an actuation geometry different from than the actuation geometry of the prior art. It is also advantageous to provide an actuating member in the form of a rocker member which is pivotally movable relative to a stationary cylindrical valve member and which pivots thereabout in response to an actuating force to move flexible valve bands from a first, closed, to a second, open, position.